S3F84B8_UM_REV 1.00
4 CONTROL REGISTERS
4-14
4.1.11 FLAGS — SYSTEM FLAGS REGISTER: D5H, BANK0
Bit Identifier
.7
.6
.5
.4
.3
.2
.1
.0
Reset Value
x x x x x x 0 0
Read/Write
R/W R/W R/W R/W R/W
R/W R R/W
Addressing Mode
Register addressing mode only
Carry Flag (C)
0
Operation does not generate a carry or borrow condition.
.7
1
Operation generates a carry or borrow into high-order bit 7.
Zero Flag (Z)
0
Operation results in a non-zero value.
.6
1
Operation results in zero value.
Sign Flag (S)
0
Operation generates a positive number (MSB = “0”).
.5
1
Operation generates a negative number (MSB = “1”).
Overflow Flag (V)
0
Operation result is
+127 and > -128.
.4
1
Operation result is > +127 or < -128.
Decimal Adjust Flag (D)
0
Completes Add operation.
.3
1
Completes Subtraction operation.
Half-Carry Flag (H)
0
No carry-out of bit 3 or no borrow into bit 3 by addition or subtraction.
.2
1
Addition generated carry-out of bit 3 or subtraction generated borrow into bit 3.
Fast Interrupt Status Flag (FIS)
0
Interrupt return (IRET) in progress (when read).
.1
1
Fast interrupt service routine in progress (when read).
Bank Address Selection Flag (BA)
0
Bank 0 is selected.
.0
1
Bank 1 is selected.